This invention relates to a method of forming a metal silicide film and, particularly, to a solid phase epitaxial method capable of easily forming a high quality monocrystalline NiSi.sub.2 or CoSi.sub.2, film, particularly adapted for use in semiconductor devices, with less influence of impurity diffusion from the NiSi.sub.2 or CoSi.sub.2 film to the Si substrate.
In semiconductor devices, a metal silicide film is used to form ohmic or Schottky barrier contacts. There have been known, as methods of growing epitaxially a monocrystalline film of NiSi.sub.2 on single crystal silicon underlie, the solid phase epitaxy in which an Ni film reacts with a Si substrate (e.g., S.Saitoh et al., Japan J. Appl. Phy., 20 (1931) p 1649), and the simultaneous deposition or co-deposition in which vaporized atoms of both Ni and Si are simultaneously deposited onto a Si substrate (e.g., J.C. Bean et al., Appl Phys. Lett., 37 (1980) p. 643). Although the solid phase epitaxy is easy in manufacturing process, it has the shortcomings that the reaction includes diffusion and hence Ni atoms may diffuse into Si substrate and that the resultant film surface has inferior morphology. Co-deposition has the advantages that the resultant silicide film can have good crystallinity, the resultant film surface can have good morphology and that less diffusion of Ni atoms occurs into the Si substrate, but it has the difficulty of maintaining the stoichiometry of Si and Ni, which imposes difficulty in practice.
There has also been known, as a method of growing epitaxially a CoSi.sub.2 monocrystalline film on a single crystal silicon underlie, the solid phase epitaxy in which a Co film reacts with a Si substrate, as described for example in R.T. Tung et al., Appl. Phys. Lett., 40 (1982) p. 684. However, this method of forming a CoSi.sub.2 film has the shortcomings of Co diffusion into Si and inferior morphology of the film surface as in the case of forming an NiSi.sub.2 film by the solid phase epitaxy.